Weight gain is observed in breast cancer patients receiving chemotherapy and is a well-known complication. Several factors that contributing to weight gain have been identified. However, there is a lack of information about factors associated with weight changes following adjuvant chemotherapy. A retrospective cohort of 200 pre- and post-menopausal Mexican patients treated for breast cancer was made. Anthropometric variables were measured before/after treatment. Biomarkers, cellular differentiation and chemotherapy were similar between groups. Weight gain occurred in 85.6% of pre-menopausal and 72.6% of post-menopausal women (p = .03). At the end of chemotherapy, weight and body mass index (BMI) did not differ significantly between pre-menopausal (69.3 ± 12.6 kg; 26.6 ± 4.8 kg/m2) and post-menopausal women (69.5 ± 10.9 kg; 27.3 ± 4.4 kg/m2) (p = .91 and 0.34). Dexamethasone doses were higher in pre-menopausal (85.7 ± 39.1 g) than post-menopausal patients (79.2 ± 22.5 g; p = .13). Weight loss was observed in 9.2% of pre-menopausal and 20.2% of post-menopausal patients (p = .04). A multivariate analysis revealed that age (OR = 2.7; 95% CI = 1.26-5.79; p = .01), menopausal status (OR = 2.29; 95% CI = 1.09-4.80; p = .03), dexamethasone dosage (OR = 2.1; 95% CI = 1.04-4.23; p = .03) and daily caloric intake (OR = 2.3; 95% CI = 1.12-5.10; p = .02) were independent variables that inducted weight gain. Pre- and post-menopausal women gained weight, but more pre-menopausal patients showed gain. An effort should be made to administer lower steroid doses to reduce weight gain.